3461. Suzanne Simard: How Do Trees Collaborate?

By Suzanne Simard and Manoush Zomorodi, NPR, June 26, 2020

Suzanne Simard

MANOUSH ZOMORODI, HOST:

It's the TED Radio Hour from NPR. I'm Manoush Zomorodi. And for most kids around the country, school is officially out of session. But unlike other summers, many kids and teens are stuck at home because of the coronavirus pandemic. And so today, we've got an episode for everyone - kids, adults, parents, teens. You are all invited on this journey because we've invited a certain dad back on the show to share the coolest things he's learned over the years here on the TED Radio Hour, topics to blow the minds of young and old. And mystery guest host, can you please introduce yourself?

GUY RAZ, BYLINE: It's the TED Radio Hour from NPR. I'm Guy Raz. Hello, Manoush.

ZOMORODI: Yay. Hello, Guy. Welcome back.

RAZ: Thank you.

ZOMORODI: OK. So, Guy, not only were you the host of this show until you so graciously handed over the reins to me, but you are also the host of a rather popular podcast for kids, right?

RAZ: Yeah. It's called Wow In The World. It's a journey through real scientific research. And it sounds a little weird, but it's like a cartoon for the ear where me and my co-host, Mindy Thomas, go on journeys into space and back in time and underwater and everywhere in between searching for incredible scientific discoveries. And it's this joyful, wonderful experience for us and hopefully for the kids who listen to the show.

ZOMORODI: Well, that includes my kids. And we sort of figured, since you and I are both home with our children this summer, we thought, you know, you'd be the perfect person to come on and curate a special summer show for the entire TED Radio Hour family. And you have so kindly brought four of your favorite segments that you did over the years. How did you even begin to choose which segments you were going to bring to us?

RAZ: Well, I think, like you probably experience, Manoush, there are a lot of TED Talks that my kids love and are really inspired by. And then there's some that, you know, of course, are sort of over their heads, right?

ZOMORODI: (Laughter).

RAZ: But I really wanted to bring segments that spoke to curiosity and the sort of the awe that kids naturally have about the world, and so that's how we kind of came up with this collection.

ZOMORODI: And I will say I did feel that way about the first segment that you brought to us. This one is called, How Do Trees Collaborate? Tell us about it.

RAZ: I love this segment so much. So basically, scientists for - basically forever thought the trees competed against each other for resources - right? - for water and sun and nutrients. And, you know, they figured that the tallest trees in the forest were the strongest trees, right? It makes sense.

ZOMORODI: Right.

RAZ: But Suzanne Simard, the scientist that we're about to hear from, she totally changed the way that scientists now think about trees because it turns out they don't compete at all. In fact, trees collaborate. They work together through this mysterious underground superhighway.

ZOMORODI: There is an entire communication network happening under our feet. Let's listen.

(SOUNDBITE OF ARCHIVED NPR BROADCAST)

RAZ: Forest ecologist Suzanne Simard had a hunch.

SUZANNE SIMARD: Yes. That's right.

RAZ: She thought that trees could talk.

SIMARD: Just imagine, like, when you're walking through the forest, you might - you hear the crunching of the twigs under your feet and the rustling of the leaves.

(SOUNDBITE OF LEAVES RUSTLING)

RAZ: But she thought - what if there's more going on?

SIMARD: Like a big chattering going on that we can't hear, that they're attuned to each other.

RAZ: Now, at the time, a team of scientists in England were wrapping up an experiment.

RAZ: And the scientists took two of these pine seedlings, these baby trees, that were in the same box, in the same dirt, and then they exposed one of these seedlings to a radioactive carbon dioxide gas.

SIMARD: Carbon-14, a radioactive carbon.

RAZ: And what they found was that some of that radioactive gas, the carbon-14, made its way into the second seedling.

SIMARD: You could visualize it. You could see it.

RAZ: And so from this experiment, it seemed that somehow, these two plants in the same dirt were connected.

SIMARD: And I thought, wow, you know, maybe this is what's going on in my forest.

RAZ: Maybe, Suzanne Simard thought, maybe all the trees in a forest are connected in a kind of network.

SIMARD: You know, like our airport system, our transportation system, our social networks.

RAZ: And maybe, she thought, all of this was happening underground.

SIMARD: When we walk through the forest, what we see as human beings - we just see these, you know, beautiful trees growing out of the ground. But we don't see that they're actually completely linked underground in this superhighway.

RAZ: So Suzanne decided to prove this underground network existed. She devised an experiment using some of the same radioactive gas, a Geiger counter to measure it and a patch of birch and fir trees.

(SOUNDBITE OF TED TALK)

SIMARD: I figured the birch and the fir would be connected in a below-ground web.

RAZ: Suzanne picks up the story from the TED stage.

(SOUNDBITE OF TED TALK)

SIMARD: And I gathered my apparatus - plastic bags and duct tape and shade cloth, a paper suit, a respirator. And then I borrowed some high-tech stuff from my university. The first day of the experiment, we got out to our plot, and I pulled on my white paper suit. I put on my respirator. I put the plastic bags over my trees. I got my giant syringes, and I injected carbon-14, the radioactive gas, into the bag of birch.

I waited an hour. I figured it would take this long for the trees to suck up the CO2 through photosynthesis, send it down into their roots and maybe shuttle that carbon below ground to their neighbors. I went to my first bag with the birch. I pulled the bag off. I ran my Geiger counter over its leaves, (imitating Geiger counter). Perfect. The birch had taken up the radioactive gas. Then, the moment of truth. I went over to the fir tree. I pulled off its bag. I ran the Geiger counter up its needles. And I heard the most beautiful sound, (imitating Geiger counter).

(LAUGHTER)

SIMARD: It was the sound of birch talking to fir. And birch was saying, hey, can I help you? And fir was saying, yeah, can you send me some of your carbon? I was so excited.

(LAUGHTER)

SIMARD: I ran from plot to plot. And I checked all 80 replicates. The evidence was clear. paper birch and Douglas fir were in a lively two-way conversation. So it turns out the two species were interdependent, like yin and yang. And at that moment, everything came into focus for me. I knew I'd found something big, something that would change the way we look at how trees interact and for us, from not just competitors but to cooperators.

(SOUNDBITE OF MUSIC)

RAZ: Now, you have to understand that Suzanne's discovery was pretty revolutionary because up until this point, most ecologists believed that trees competed against each other, that their world was, like, a Darwinian struggle with winners and losers.

SIMARD: Yeah, you know, that they're competing for light and water and nutrients.

RAZ: And that the strongest trees were the ones that grew tall, the ones that dominated the canopy and took all the resources. But Suzanne's experiment showed that something else was true.

SIMARD: They're actually sending messages back-and-forth that balances the resource distribution among the community.

RAZ: In other words, trees aren't just connected. They're actually sharing resources with each other.

SIMARD: So what we found initially, if one tree had a lot of water in it or a lot of nitrogen or had high photosynthetic rate and if one tree is sick, then the neighboring tree shuttles more of those nutrients to that suffering tree.

RAZ: And when you say communicate, do they actually communicate? Like, do they warn each other about, like, a fire or an invasive species or something?

SIMARD: Yes. So if one tree gets damaged by, say, mountain pine beetle, the injured seedling will up its defense enzymes. And then the receiving tree will then increase its defense enzymes because it knows now that there is some kind of damaging agent around.

RAZ: Wow. So how are they doing this? Like, how are they communicating through an underground network?

SIMARD: So they're physically connected by these microscopic fungi. And...

RAZ: So mushrooms?

SIMARD: Yes, you're right. We call them hyphae or mycelium. In fact, like, if you were to, you know, peel back the surface of the forest floor, you'll see the fungi that are linking these trees together. They're very visible. And it's these white and yellow, different colored threads that are - they look like, you know, sewing threads. But they're fungal threads. And they're crisscrossed and going off in multiple directions. And they work together to create a very, you know, a very complex web. And they're in constant communication between all the trees.

(SOUNDBITE OF TED TALK)

SIMARD: Forests aren't simply collections of trees. They're complex systems with hubs and networks that overlap and connect trees and allow them to communicate, and they provide avenues for feedbacks and adaptation. And this makes the forest resilience. That's because there are many hub trees and many overlapping networks, but they're also vulnerable because hub trees are not unlike rivets in an airplane. You can take out one or two, and the plane still flies. But you take out one too many or maybe that one holding on the wings, and the whole system collapses. Well, you know, the great thing about forests as complex systems is they have enormous capacity to self-heal.

In our recent experiments, we found with retention of hub trees and regeneration to have diversity of species and genes and genotypes, that these mycorrhizal networks, they recover really rapidly. We need to regenerate our forests with a diversity of species and genotypes and structures by planting and allowing natural regeneration. We have to give Mother Nature the tools she needs to use her intelligence to self-heal, and we need to remember that forests aren't just a bunch of trees competing with each other. They're super cooperators. Thank you.

(APPLAUSE)

ZOMORODI: Oh, so good, Guy. Do you think about this segment, like, every time (laughter) you go for a walk...

RAZ: Yeah.

ZOMORODI: ...Through a forest, I'm guessing?

RAZ: Yeah. Yeah. I - all the time. I live in California, in Northern California. And every time I'm in a redwood forest, I think about Suzanne Simard and how trees and forests are models for us, for human beings.

ZOMORODI: In terms of the resiliency that they can help build in groups. I mean, I feel...

RAZ: Yeah.

ZOMORODI: ...Like this idea of helping each other, having that cooperation in our roots is actually really, really wonderful to think about in light of what's been going on in the world right now and...

RAZ: Yeah.

ZOMORODI: ...How much we need our neighborhoods and our communities to be resilient and help each other.

RAZ: Yeah. I mean, we will all, at some point in our lives, need help. And we can all also help. It's an incredibly simple idea, but it's also so powerful. And Suzanne's research just puts it out into the world in such a beautiful way.

(SOUNDBITE OF MUSIC)

ZOMORODI: OK. When we come back, Guy, we're going to go from the forest to the Caribbean Sea and some dolphins who actually have some things to say and communicate. You want...

RAZ: All right.

ZOMORODI: ...To make some clicking dolphin noises for me here?

RAZ: (Imitating dolphin).

ZOMORODI: I'm Manoush Zomorodi. And you're listening to the TED Radio Hour from NPR. Stay with us.

RAZ: (Imitating dolphin).

3460. A reply to John Molyneux and Michael Löwy on Degrowth

By Louis Proyect, The Unrepentant Marxist, December 18, 2020

Louis Proyect

Generally speaking, my defense of degrowth is mounted against the ecomodernists at Jacobin/Catalyst: Leigh Phillips and Matt Huber, who both stand on Marxist orthodoxy, at least in their view. Although I’ve never answered him specifically, Neo-Keynesian Robert Pollin has staked a position against degrowth in the July-August 2018 NLR. If you’re interested in this debate, I recommend tracking down the NLR and to look for articles by Phillips and Huber on Jacobin and Catalyst.

This is the first time I will be responding to people much closer to me ideologically, John Molyneux, an ex-member of the British SWP, and Michael Lowy, a longtime member of the Mandelista Fourth International. Molyneux’s article is titled “Growth and De-growth: What should ecosocialists say” and can be read on the Global Ecosocialist Network. Lowy’s article is titled “Ecosocialism: A Vital Synthesis” and appears on Ian Angus’s Climate and Capitalism website.

Let me turn to Molyneux first, if for no other reason that the title of his article indicates a willingness to take on his ideological adversaries head-on.

Unfortunately, Molyneux cherry-picks an intellectual exercise from leading degrowth theorist Giorgos Kallis and proceeds to trash what amounts to a straw-man. In an article that appeared in “The Internationalist”, Kallis wrote:

The Left has to liberate itself from the imaginary of growth. Perpetual growth is an absurd idea (consider the absurdity of this: if the Egyptians had started with one cubic metre of stuff and grew it by 4.5% per year, by the end of their 3,000-year civilization, they would have occupied 2.5 billion solar systems.). Even if we could substitute capitalist growth, with a nicer, angelic socialist growth, why would we want to occupy 2.5 billion solar systems with it?

This is what they call a hypothetical and it is foolish to use it to represent degrowth analysis, which is completely steeped in the actual ecological limits we are dealing with. Kallis is an ecological economist by profession and is involved in studies of water development and urbanization, so turning him into a promoter of specious theories based on Egypt’s alternative history does not do him justice.

The remainder of Molyneux’s article is a rehash of the arguments I’ve heard and made about the anarchy of capitalist production for the past 53 years. For example, “If the productive forces constitute society’s general capacity to produce then their development or advance need not necessarily result in more production of things at all but might equally result in producing the same amount in less time. Marx, himself, put a lot of emphasis on this economy of labour time as he saw it has having the potential to free human beings from necessary labour, reduce the working week and enhance human freedom.”

Well, who can argue with that? Unquestionably, socialism will be a more rational system. Commodity production based on profit is the number one cause of environmental despoliation. If the economy is based on the production of use-values, you can finally use science and humanism to create a livable world.

Molyneux proceeds to define some of the norms we can expect under world ecosocialism. This one stuck out for me: “The extensive retrofitting of homes”. I am not sure what this means exactly but it would point to the banning of any house or apartment over 3,000 square feet for a family of four. I’m definitely for that but within such an advanced new way of sheltering, how do we create the furniture that people need for a modicum of comfort? We certainly need chairs, tables, beds, desks, and bookshelves, don’t we? Can we have a socialist Ikea that supplies such basics?

Over the past four decades, China has tried to make sure that its citizenry can live a comfortable middle-class existence. That has meant becoming the world’s largest importer of wood. (The United States is second.) It is also the largest exporter — turning much of the wood it imports into products headed to Home Depots and Ikeas around the world.

The irony is that Ikea brags about its environmentalist values. Its website states: “We’re also working towards 100% renewable energy – producing as much as we consume in our operations – and sourcing all of our wood from more sustainable sources by 2020.” All that is well and good but the inexhaustible demand for cheap furniture will simply lead other corporations to rely on Chinese suppliers. That’s how capitalism works, after all—supply and demand. So efficient at reducing forests to toothpicks.

Now, under world ecosocialism, how could you continue to provide the wood needed for the average household without encroaching on the forests and hence the risk of a new pandemic? For pete’s sake, Marxism is a powerful tool but it cannot produce wood out of thin air. That’s the purview of the sorcerer’s apprentice and you saw how much trouble Mickey Mouse got into.

Degrowth is completely focused on the question of how humanity can not only survive into the 22^nd century but how can civilization continue until the planet dies due to astrophysical realities. It poses solutions based on the needs of a modest life-style that while giving up on SUV’s and all the other crap can allow the full development of the human being, who might have to work 10 hours a week while painting landscapes or growing orchids the rest of the time. That means addressing the population question that people like Molyneux recoils from. There is scant attention to that in his article, with this being typical:

In particular we should also challenge the idea, implicit in the arguments of many ‘degrowthers’, especially those that favour population control , that all human activity, indeed all human existence, is inherently damaging to nature.

I don’t know about “many” degrowthers. I do want to know, however, whether Molyneux has engaged at all with the numbers that both Kallis and Jason Hickel have crunched. Let me direct him to something that Hickel wrote to get started. This is the heart and soul of degrowth scholarship, not Kallis’s intellectual exercise about Egypt:

Adopting a higher poverty line makes it more difficult to end poverty while remaining within planetary boundaries. At the US$7.40 line, Belarus is the most promising, with minimal social shortfall (a score of 0.98) excluding qualitative indicators, but its average biophysical score is 1.64. Of the nations that achieve all non-qualitative social thresholds, the most biophysically efficient is Oman, which has an average biophysical score of 2.66. In other words, given the existing best-case relationship between resource use and income, achieving a good life for all with an income threshold of US$7.40 per day would require that poor nations overshoot planetary boundaries by at least 64% to 166%.

Of course, Hickel could have just said that ecosocialism will solve these problems with scarcely a need to figure out the desperately important balance between humanity and nature under conditions of declining water, soil and climate. I hope he continues on his current trajectory.

Turning now to Lowy’s article, it is closely related to Molyneux’s with the idea of socialism replacing capitalism on a world-scale being the solution to our problems. He writes:

The issue of economic growth has divided socialists and environmentalists. Ecosocialism, however, rejects the dualistic frame of growth versus degrowth, development versus anti-development, because both positions share a purely quantitative conception of productive forces. A third position resonates more with the task ahead: the qualitative transformation of development.

A new development paradigm means putting an end to the egregious waste of resources under capitalism, driven by large-scale production of useless and harmful products. The arms industry is, of course, a dramatic example, but, more generally, the primary purpose of many of the “goods” produced — with their planned obsolescence — is to generate profit for large corporations. The issue is not excessive consumption in the abstract, but the prevalent type of consumption, based as it is on massive waste and the conspicuous and compulsive pursuit of novelties promoted by “fashion.” A new society would orient production towards the satisfaction of authentic needs, including water, food, clothing, housing, and such basic services as health, education, transport, and culture.

So,  “A new society would orient production towards the satisfaction of authentic needs, including water, food, clothing, housing, and such basic services as health, education, transport, and culture.” Let’s start with water.

Okay, how is ecosocialism going to generate groundwater that is the key to sustainable agriculture? Will making the Ogallala Aquifer people’s property somehow overcome the ecological limits on a resource that took thousands of years to accrue? Natural forces produced it and it was used to grow the wheat that is a necessity for urban life. You can take the position that cattle and wheat have to go but any foodstuff is going to have to rely on water. Even under the best of conditions, water can become scarce because it is serving a population that far exceeded the numbers that lived in North America 30,000 years ago. Since 1950, agricultural irrigation has reduced the saturated volume of the aquifer by an estimated 9%. Once depleted, the aquifer will take over 6,000 years to replenish naturally through rainfall. (Wikipedia) Instead of bad-mouthing Giorgos Kallis’s speculation on Egypt, Molyneux and Lowy could both benefit from his work on water conservation.

I consider Molyneux and Lowy’s attempt to debunk degrowth feeble at best. I have been following debates within the left on ecology for the past 30 years and have been shocked by the way that long-time Marxists just skate over the surface of degrowth scholarship. My advice to them and others is to put the Marxist verities on the back burner, roll up their sleeves, and begin to delve into the details of how the human race can continue with the current set-up. Socialism can do many things but it cannot produce wood and water out of thin air.

3459. How Stalinism Saved the US Democrats

By Emma Norton, Red Flag, December 16, 2020

Franklin Delano Roosevelt, 32nd president of the United States from 1933 until his death in 1945 is now once again fashionable in the U.S. socialist circles. 

The Democratic Party of the US, along with its legions of capitalist donors, supporters in the state bureaucracy, liberal NGOs and union officials, serves to slap an occasionally liberal gloss on unbridled capitalism. Throughout US history, the Democrats have been called upon to coopt and nullify progressive mass movements. Yet swathes of the socialist left find it impossible to break from the Democrats, and the idea that it is permissible to campaign for them is deeply entrenched. But Stalinism is no alternative to Democratic liberalism. Ironically, it was Stalinism that helped the workers’ movement of the US into the abusive arms of the Democrats.

Until the middle of the 1930s, few socialists in the world would have dared support the candidates or program of a capitalist party like the Democrats. Since the 19th century, the socialist movement had been riven with debates about the necessity for revolution. But there was widespread agreement on the need for working-class independence from other classes, a concept that Marx and Engels considered essential to revolutionary theory and practice.

The pair concluded from their experience of the 1848 revolutions that the working class must be organisationally and politically independent of other classes, and that elections were an important avenue for expressing that independence. As Marx put it in his “March Address” of 1850:

“Even where there is no prospect of achieving their election the workers must put up their own candidates to preserve their independence, to gauge their own strength and to bring their revolutionary position and party standpoint to public attention. They must not be led astray by the empty phrases of the democrats, who will maintain that the workers’ candidates will split the democratic party and offer the forces of reaction the chance of victory. All such talk means, in the final analysis, that the proletariat is to be swindled.”

Instead of accepting the rhetoric of political parties and individuals at face value, Marx and Engels analysed their class basis. The interests of the capitalists, even their liberal wing, would always clash with those of the working class. They “diverge at an angle of 180 degrees”, as Trotsky was to put it almost 90 years later. Marx and Engels concluded that, even if the working class needed to cooperate with other classes for some common goal, it would need to organise separately and always put forward its own political program if it wished to avoid being sidelined, compromised or crushed.

The Socialist Party of America understood this basic principle. The party, formed in 1901, recognised that bourgeois parties like the Democrats and the Republicans were the enemies of workers, and that socialists had to argue this. They ran socialist candidates in elections against both major parties, including in the presidential race. They won dozens of mayoral and state governor contests, and gained around 6 percent of the presidential vote. They maintained their critical line in the face of enormous pressure to endorse Democratic President Woodrow Wilson during his 1916 re-election campaign. Wilson was a darling of liberals; after his re-election, he would lead the US into World War I. The socialists went on to oppose virulently America’s entrance into the war, landing many of their members, from both the left and the right, in jail. The popular radical Eugene Debs secured a million votes in the next presidential election from his prison cell.

By the Second World War, this admirable commitment to independent workers’ organisations had become its opposite for socialists around the world. Many would be drawn into campaigning uncritically for liberal bourgeois parties and governments. Why?

Stalin’s government in Russia, and the Stalinist Communist parties around the world, played the leading role in convincing millions of working-class socialists to subordinate their parties, unions and their own class interests to the will of the “progressive” capitalists and middle-class liberals.

The new strategy was called the Popular Front. The Stalinists claimed that the global fascist threat, which had multiplied with the defeat of the German and then Spanish revolutions, had to be met with a broad anti-fascist coalition that included liberals. The goal was to defend liberal and reformist governments rather than intensifying working-class struggle. Instead of fighting fascism through working-class organisation and defence of democratic rights even up to the point of revolution, Stalin’s movement focused its energies on constructing and promoting capitalist governments.

Prior to the adoption of the Popular Front, Stalin’s regime in Russia had pursued a rhetorically militant policy for several years. Claiming that global capitalism was on the verge of collapse, the Communists insisted that all liberals, social democrats and the workers loyal to them were no different from fascists, and they would all soon be overthrown in a victorious revolution. Everywhere Communists built their own unions separate from the rest of the workers’ movement and refused to unite the working class for joint action against the growing far-right.

The policy helped bolster the power of Stalin’s bureaucracy over the Russian state and the foreign Communist parties. Anyone who refused to go along with the sectarian mania was either purged from the Communist movement or, in Russia, imprisoned or executed. By 1934, Stalin’s regime in the USSR had largely eradicated any opposition to his rule. At the same time, Hitler’s government in Germany posed a military threat to the USSR. Instead of strategising to overthrow Hitler with a workers’ revolution, Stalin sought diplomatic and military alliances with imperialist governments like France, Britain and the US. The previous theory had declared the US president a “social fascist”. Now Stalin did a complete about-face. The Popular Front became the new policy of the Communist International: it demanded that Communist workers play nice with their ruling classes. The Popular Front represented the further subjugation of the international workers’ movement to the interests of the Russian state bureaucracy, and it revealed the extreme counter-revolutionary role of Stalinism.

In the US, the Stalinists led the most militant workers’ movement in US history into a disastrous alliance with liberals, union bureaucrats and the Democratic Party. This unsavoury alliance is often referred to as the “New Deal coalition”. As the aristocratic President Franklin Roosevelt tried a series of economic and social measures to jump-start the economy, he also had to try to contain a growing militant strike wave in industry. State and city governments and bosses, many of them Democrats, used police violence and the National Guard to smash strikes, while the federal government also promoted class collaboration, arbitration and compromise. Roosevelt coopted the leadership of an emerging radical union movement and channeled that energy into support for the Democratic Party.

Democrats like Roosevelt could always be expected to play this role. But in a twisted way, the Communists were better placed than anyone to convince worker militants of the virtues of Roosevelt’s New Deal coalition.

Throughout the 1930s upsurge of workers’ struggle, which led to the creation and growth of the CIO union federation, the Communist Party had built an impressive multiracial organisation of worker militants, numbering in the tens of thousands. They had an important base among industrial workers who led sit-down strikes from 1935 to 1937 in steel, rubber and other industries. They accepted many full-time positions in the growing union bureaucracy, leading about 40 percent of the new industrial unions by 1937. Both the union bureaucracies and the Democrats realised the value of Stalinists in helping to wind up the wave of struggle. Luckily for them, the Communists had by then turned sharply towards the Popular Front and were desperate to be accepted into the liberal alliance. Much of their focus was on supporting the Democratic Party. By 1938, Communist leader Eugene Dennis was arguing that in the US, the Popular Front could “take the form of a political federation, operating insofar as electoral activity is concerned, chiefly through the Democratic Party”. 

The Communists argued that the Democrats and the New Deal coalition were the only thing preventing America’s collapse into fascism. In 1938, Communist leader Earl Browder said that democracy was “fighting for its life” in much of the capitalist world: “It can survive only to the degree to which there are successfully carried out programs such as those of ... the Committee for Industrial Organization and the economic reforms and peace program of President Roosevelt”.

Roosevelt’s “peace program” would soon include an unprecedented military build-up, participation in World War II and an oppressive division of the world into “spheres of influence”.

Around the world, the Stalinist Popular Front did nothing to prevent the rise of fascism. In Spain, the Communists hoped to keep the bourgeois Republican government in power during the fight against Franco’s fascist forces. In the process, they wilfully destroyed the workers’ militias and collectives and wrecked the possibility of social revolution. With much of the population unable to defend themselves, and the rest disillusioned, Franco’s victory was complete. Fascism reigned in Spain for 30 years. In the US, fascists were not on the verge of state power. Roosevelt’s New Deal administration was the immediate threat to the continued strength of the workers’ movement—and his warmongering was the greatest threat to democracy and freedom.

The Communists argued that only the Democrats would defend workers’ rights to collective bargaining and union recognition. In fact, workers made the most gains precisely when they didn’t rely on Roosevelt and fought back against the forces of the state. A Roosevelt presidency was no guarantee of union rights. As the struggle was wound up in the late 1930s, the bosses pushed back against collective bargaining, and company unions grew. The Democratic-controlled courts ruled sit-down strikes illegal. 

Nor did the commitment to the New Deal result in new social reforms after 1935. With the onset of another economic downturn, Roosevelt slashed poor relief and the public works program for the unemployed in 1938 and 1939, unemployment rose and the bosses clawed back wages and union rights. But by this time, the Communists had convinced a generation of working-class militants that the most important political task of the workers’ movement was to promote political loyalty to Roosevelt’s capitalist Democrats.

Because of their sycophantic attitude towards liberals, the Communists began to lose influence among rank-and-file workers, even as their party grew by attracting moderate liberals and middle-class sympathisers. The Communists had consciously abandoned their campaign organisations within the working class by 1938, so as not to seem threatening to the CIO or the Democrats. The Black Communist leader Harry Haywood reflected years later in his autobiography, “[T]he tendency to subordinate the class struggle to Roosevelt’s New Deal policy had manifested itself earlier in the liquidation of the Party’s factory units, shop papers and trade union fractions”.

Stalinist support for the Democrats helped entrench the two-party system in the US and complete the historic “realignment” that shuffled liberals, Blacks, migrants and the bulk of unionised workers into the Democratic camp. This did not usher in a paradise of social reform. Black people, migrants and workers all gained very little from a prolonged period of Democratic presidencies, except that which they won by struggle. The fact that the oppressed felt that their lives were tied to the electoral fortunes of the Democrats served only to dampen struggle.

This cooption was not a foregone conclusion. In the rebellious atmosphere of the 1930s there was a groundswell of support for a working-class alternative to the major parties. Meetings of miners, smelters, sleeping car porters, textile workers and southern farmers all voted to form a workers’ party. A similar motion passed unanimously at a meeting of the United Auto Workers, who even voted down a resolution supporting Roosevelt for president in 1936. A Gallup Poll conducted in 1937 reported that at least 21 percent of the American population supported the formation of a national “farmer-labor party”. The bureaucrats of the new industrial unions worked closely with the Communist Party to put an end to the agitation for a new, independent workers’ party.

Perhaps the most sickening practical application of Popular Front-style politics came during World War Two. The American Communists fell into outright sycophancy after the Soviet Union joined the war in June 1941, adopting an ultra-patriotic stance. Communist leader Earl Browder argued that “the main sacrifice” for the war effort must come from workers, declaring that “class division or political groupings have no significance now”. They supported and rigorously enforced a no-strike pledge and production speed-ups. This fervent patriotism and uncritical support for Roosevelt did not reflect the mood of rank-and-file unionists, who continued to strike in spite of the Stalinists. The Communist Party publicly condemned strikes in war industries, even slandering the 1943 United Mine Workers strike as “pro-Nazi”.  

Stalinist parties  played this treacherous role around the world. The sum of their efforts was to wind up revolutionary workers’ movements, normalise left-wing support for capitalist parties, promote reformism within the working class and marginalise left-wing opposition to Western imperialism in World War II. The British Communist Party sang the praises of Winston Churchill, the Tory and prewar Nazi sympathiser. Even after the war, they supported Churchill, supposedly engaged in a fight against the “reactionary sections of capitalism”, and offered to extend the no-strike pledge. 

The Stalinists facilitated a historic shift in the workers’ movement towards open support for bourgeois parties and liberals. Everywhere, the results were dire. Radical explosions of struggle, and even revolutions, were subjugated to the interests of capitalist parties, who crushed and tamed them in equal measure. The legacy of those years in America is a left that consistently chains itself to the chariot wheels of the Democratic Party, still regurgitating many of the same arguments used by the Stalinists in the late 1930s.

3458. Quantum Physics: A Very Short History

By Richard Webb, New Scientist,December 2020

What is quantum physics? Put simply, it’s the physics that explains how everything works: the best description we have of the nature of the particles that make up matter and the forces with which they interact. Quantum physics underlies how atoms work, and so why chemistry and biology work as they do. You, me and the gatepost – at some level at least, we’re all dancing to the quantum tune. If you want to explain how electrons move through a computer chip, how photons of light get turned to electrical current in a solar panel or amplify themselves in a laser, or even just how the sun keeps burning, you’ll need to use quantum physics. 

The difficulty – and, for physicists, the fun – starts here. To begin with, there’s no single quantum theory. There’s quantum mechanics, the basic mathematical framework that underpins it all, which was first developed in the 1920s by Niels Bohr, Werner Heisenberg, Erwin Schrödinger and others. It characterises simple things such as how the position or momentum of a single particle or group of few particles changes over time. 

But to understand how things work in the real world, quantum mechanics must be combined with other elements of physics – principally, Albert Einstein’s special theory of relativity, which explains what happens when things move very fast – to create what are known as quantum field theories. 

Three different quantum field theories deal with three of the four fundamental forces by which matter interacts: electromagnetism, which explains how atoms hold together; the strong nuclear force, which explains the stability of the nucleus at the heart of the atom; and the weak nuclear force, which explains why some atoms undergo radioactive decay. 

Over the past five decades or so these three theories have been brought together in a ramshackle coalition known as the “standard model” of particle physics. For all the impression that this model is slightly held together with sticky tape, it is the most accurately tested picture of matter’s basic working that’s ever been devised. Its crowning glory came in 2012 with the discovery of the Higgs boson, the particle that gives all other fundamental particles their mass, whose existence was predicted on the basis of quantum field theories as far back as 1964. 

Conventional quantum field theories work well in describing the results of experiments at high-energy particle smashers such as CERN’s Large Hadron Collider, where the Higgs was discovered, which probe matter at its smallest scales. But if you want to understand how things work in many less esoteric situations – how electrons move or don’t move through a solid material and so make a material a metal, an insulator or a semiconductor, for example – things get even more complex. 

The billions upon billions of interactions in these crowded environments require the development of “effective field theories” that gloss over some of the gory details. The difficulty in constructing such theories is why many important questions in solid-state physics remain unresolved – for instance why at low temperatures some materials are superconductors that allow current without electrical resistance, and why we can’t get this trick to work at room temperature. 

But beneath all these practical problems lies a huge quantum mystery. At a basic level, quantum physics predicts very strange things about how matter works that are completely at odds with how things seem to work in the real world. Quantum particles can behave like particles, located in a single place; or they can act like waves, distributed all over space or in several places at once. How they appear seems to depend on how we choose to measure them, and before we measure they seem to have no definite properties at all – leading us to a fundamental conundrum about the nature of basic reality. 

This fuzziness leads to apparent paradoxes such as Schrödinger’s cat, in which thanks to an uncertain quantum process a cat is left dead and alive at the same time. But that’s not all. Quantum particles also seem to be able to affect each other instantaneously even when they are far away from each other. This truly bamboozling phenomenon is known as entanglement, or, in a phrase coined by Einstein (a great critic of quantum theory), “spooky action at a distance”. Such quantum powers are completely foreign to us, yet are the basis of emerging technologies such as ultra-secure quantum cryptography and ultra-powerful quantum computing. 

But as to what it all means, no one knows. Some people think we must just accept that quantum physics explains the material world in terms we find impossible to square with our experience in the larger, “classical” world. Others think there must be some better, more intuitive theory out there that we’ve yet to discover. 

In all this, there are several elephants in the room. For a start, there’s a fourth fundamental force of nature that so far quantum theory has been unable to explain. Gravity remains the territory of Einstein’s general theory of relativity, a firmly non-quantum theory that doesn’t even involve particles. Intensive efforts over decades to bring gravity under the quantum umbrella and so explain all of fundamental physics within one “theory of everything” have come to nothing. Meanwhile, cosmological measurements indicate that over 95 percent of the universe consists of dark matter and dark energy, stuffs for which we currently have no explanation within the standard model, and conundrums such as the extent of the role of quantum physics in the messy workings of life remain unexplained. The world is at some level quantum – but whether quantum physics is the last word about the world remains an open question.

3457. Core Questions in Domestication Research

By Melinda A. Zeder, Proceedings of National Academy of Sciences of the United States of America, March 17, 2015

Significance

Domestication of plants and animals marks a major transition in human history that represents a vibrant area of interdisciplinary scientific inquiry. Consideration of three central questions about domestication—what it is, what it does, and why it happened—provide a unifying framework for diverse research on the topic. Domestication is defined in terms of a coevolutionary mutualism between domesticator and domesticate and is distinguished from related but ultimately different processes of management and agriculture. Domestication results in a range of genotypic, phenotypic, plastic, and contextual impacts that can be used as markers of evolving domesticatory relationships. A consideration of causal scenarios finds greater empirical support for explanatory frameworks grounded in niche-construction theory over those derived from optimal foraging theory.

Abstract

The domestication of plants and animals is a key transition in human history, and its profound and continuing impacts are the focus of a broad range of transdisciplinary research spanning the physical, biological, and social sciences. Three central aspects of domestication that cut across and unify this diverse array of research perspectives are addressed here. Domestication is defined as a distinctive coevolutionary, mutualistic relationship between domesticator and domesticate and distinguished from related but ultimately different processes of resource management and agriculture. The relative utility of genetic, phenotypic, plastic, and contextual markers of evolving domesticatory relationships is discussed. Causal factors are considered, and two leading explanatory frameworks for initial domestication of plants and animals, one grounded in optimal foraging theory and the other in niche-construction theory, are compared.

• domestication
• mutualism
• genetic impacts
• ecophenotypic impacts
• niche-construction theory

The domestication of plants and animals marks a major evolutionary transition in human history—one with profound and lasting global impacts. The origins of domestication—when and where, how, and why our ancestors targeted plant and animal species for domestication—is an enduring and increasingly active area of scientific inquiry for researchers from many different disciplines. Enhancing present-day productivity of long-standing and recently domesticated species and exploring social and biological issues surrounding their role in feeding rapidly expanding global populations are topics of pressing concern. The volume and breadth of domestication research is underscored by a keyword search on the term “domestication” for the year 2013 which yielded a total of 811 papers in more than 350 different journals (Table S1), including 42 articles published in PNAS (Table S2).

Given the large and growing number of studies on domestication across a wide array of disciplines, it is worthwhile to address three central questions. (i) Is there a definition of domestication applicable to both plants and animals from the distant past to present day that distinguishes domestication from related processes of resource management and agriculture? (ii) How does domestication change both the domesticate and domesticator, and how can we track these changes through time? (iii) Why did humans domesticate plants and animals, and are there common causal factors that underlie the process of domestication wherever it takes place?

Defining Domestication and Distinguishing Domestication from Management and Agriculture

There is a surprising lack of consensus on how to define domestication. Beyond agreeing that it involves a relationship between a domesticator and a domesticate, there is little agreement on what this relationship entails or how and when it results in the creation of a domesticated plant or animal. Domestication is frequently defined from the perspective of the domesticator, emphasizing the role of humans in separating a target domesticate from free-living populations and assuming mastery over all aspects of its life cycle (1). Domestication has also been viewed as a mutualistic, symbiotic relationship that benefits both domesticator and domesticate (2), with domesticates sometimes considered as having benefited more than their human partners (3). Some researchers see genetically driven change in a domesticate’s phenotype as the central defining characteristic of domestication (4). Others maintain that such an emphasis misdirects attention to a narrow aspect of domestication that may vary from case to case, or seem not to occur at all (5). Instead of focusing on the effects of domestication, some argue that domestication should be defined in terms of the relationship between humans and target species that causes genetic and other responses. This shift in focus sometimes results in a broadening of the definition of domestication to cover a much wider array of human interactions with plants and animals (6), including declaring a species domesticated “whenever another species knows how to harvest it” (5), or proposals for replacing the term domestication with less prejudicial ones such as “cultural control” (7).

Against this confusing backdrop of conflicting approaches to conceptualizing domestication, the following definition is offered: Domestication is a sustained multigenerational, mutualistic relationship in which one organism assumes a significant degree of influence over the reproduction and care of another organism in order to secure a more predictable supply of a resource of interest, and through which the partner organism gains advantage over individuals that remain outside this relationship, thereby benefitting and often increasing the fitness of both the domesticator and the target domesticate.

This distinctive kind of mutualism is not restricted to humans and domestic crops and livestock but is well documented in nonhuman species, especially among a number of social insect domesticators and their plant and animal domesticates (8). Domesticatory relationships between organisms such as leaf cutter ants and fungi, however, arise through a gradual coevolutionary process of selection operating on mutation-induced behavioral, physiological, and morphological changes in both partners that are passed on to offspring through the hit-or-miss process of sexual reproduction. Humans, in contrast, are able to opportunistically invent and modify behaviors that enhance benefits gained from coevolutionary relationships with target species, and, most importantly, humans are able to transmit behaviors that meet perceived goals not only to their offspring but more widely to others outside their immediate kin group through social learning (9). This human ability to choose between genetic variants of partner species, to leave one relationship in favor of another, to consciously manipulate a symbiont’s life history to the domesticator’s benefit, is the key feature that distinguishes human domesticatory relationships from those between nonhuman species (8). Contra researchers who reject the role of deliberate intent or agency in early human domesticatory relationships (3, 10), it is precisely this capacity for goal-oriented behavior that makes human-driven domestication qualitatively different from that between nonhuman partners. Clearly the goal of these behaviors was not to deliberately, in a teleological fashion, domesticate another species or invent agriculture. However, decisions to modify environments, move plants and animals to new environments, and selectively harvest and breed certain species—decisions that initiated and fostered the development of the mutualistic relationships at the core of domestication—were, nonetheless, arrived at consciously with defined goals in mind made possible by the uniquely human ability to spontaneously invent new behaviors and to pass them on to others (11).

The definition offered here does not encompass genetic or plastic responses to domestication in either the domesticator or domesticate. Defining domestication in terms of these changes begs the question of how many genes and how much phenotypic change is needed to distinguish between domestication and other kinds of adaptive responses that might occur as the result of manipulation of a species or its environment. Similarly, defining domestication in terms of the degree to which the plant or animal is incorporated into human socioeconomic organization (12) misdirects attention toward aspects of the relationship that are not universal and away from the relationship that more properly lies at the center of any definition of domestication.

Although the proposed definition focuses on the relationship between partners rather than on the biological or cultural outcomes of the relationship, it also differs in significant ways from definitions that emphasize the domesticator’s role in controlling or harvesting the domesticate. Such definitions are actually more relevant to the term “management,” which for purposes here can be defined as: the manipulation of the conditions of growth of an organism, or the environment that sustains it, in order to increase its relative abundance and predictability and to reduce the time and energy required to harvest it.

This basic “niche-constructing” behavior is widely practiced by humans and nonhuman species and is argued to be a major driver of evolution in both the niche-constructing species and other species living within the constructed niche (13). Some form of management is an essential prerequisite of domestication, but it is not sufficient for the development of a domesticatory relationship. Management that does not substantially alter the selective pressures on the managed resource from those experienced in a free-living state or that does not persist over several generations of the managed population (i.e., that relies on continuous restocking from free-living populations without breeding or cloning managed individuals) will likely not lead to domestication. In order for management to result in domestication, a sustained multigenerational relationship must develop between the manager and the managed from which both reap mutual, although not necessarily symmetrical, benefits. Sustaining the relationship over the long term requires that both partners undergo modifications (genetically driven or facultative) that enhance the benefits each accrues. In an evolving human/plant domesticatory relationships, for example, the development of artificial irrigation benefits the human partner by increasing the yield of the plant, while also increasing the irrigated plant’s reproductive success over populations situated outside the irrigation system. Adaptations that might make a plant a more attractive partner include alterations in physiological functions controlling ripening synchrony that benefit humans by making harvest schedules more predictable, while increasing the probability that individuals ripening at the same time dominate seed stock reserved for next year’s planting. Such modifications not only increase mutual benefits to both partners, they may also make one or both more dependent on the other, limiting opportunities to leave the partnership.

Another feature that distinguishes domestication from resource management is the capacity of each partner to make modifications that help sustain the relationship. For humans this might involve assessing whether the returns of a managed resource justify continuing investment, especially in light of the returns from other available resources whose exploitation carry different or perhaps conflicting requirements. Traits that make a plant or animal responsive to management are key prerequisites in a successful domesticate. The ability to colonize open, disturbed anthropogenic habitats is one such trait in plants (14); in animals these traits include a hierarchical social structure and, especially, lower reactivity to humans (15). Another adaptive feature in a successful domesticate is the capacity for rapid response to selective pressures under domestication (genetically driven or plastic) in ways that enhance the benefits they and their partners derive from the relationship.

The pathways that humans and target species follow from initial management into domestication are shaped by a number of contingencies affecting both partners and can be broadly classified into three types: (i) a commensal pathway in which the plant or animal first moves into an anthropogenic habitat and later develops a two-way partnership with humans, (ii) a prey or harvest pathway initiated by a human interest in enhancing the yield or predictability of a resource provided by target species, and (iii) a directed pathway in which humans deliberately set out to domesticate a species (15). Species following the first two pathways tend to possess more traits that make them suitable candidates for domestication. Species on directed pathways, in contrast, likely possess barriers to domestication that require more knowledge on the part of humans to overcome. This is the pathway taken in all of the more recent domestication efforts where domestication may involve more advanced technologies (e.g., artificial insemination or genetic manipulation).

Some species, moreover, possess behavioral or morphological characteristics that pose insurmountable barriers to domestication, despite human efforts at manipulation that in other species led to domestication. Although there is some evidence of tentative steps toward management of gazelle in the early Neolithic of the southern Levant (16), for example, the animal’s well-developed flight reflex and resistance to captive breeding precluded the relationship between humans and gazelle from moving beyond the initial audition phase (15). On the human side of the equation, potential domesticates might be abandoned in favor of other equally attractive candidate species that subsequently move on become to full-fledged domesticates. Wild oats, barley, and emmer wheat, for example, were each intensively used and likely managed in some way in the Levant, but oats lagged far behind barley and emmer in developing into a domesticate (17). There are also examples of multiple independent domestications of a single species following very different pathways in different regions (18, 19).

Just as some level of management is an essential precursor to domestication, the presence of domesticates is a prerequisite for agriculture. Human utilization of one or more domesticates, however, does not constitute agriculture. Instead, agriculture is distinguished by the degree of dependence on domesticates (20) and is defined here as: a provisioning system based primarily on the production and consumption of domesticated resources.

Not only are the terms “domestication” and “agriculture” not interchangeable, as often implied (10), agriculture is not an automatic outcome of domestication. In virtually every instance of agricultural emergence there is a long delay of up to a thousand years or more between initial domestication and the development of fully formed agricultural systems (20, 21). Low-level food-producing economies that include a mix of domesticates and an array of loosely managed or entirely free-living resources, moreover, have existed for millennia without ever developing into agricultural economies (20). There are also examples of societies that abandoned a fully agricultural way of life in favor of broad-spectrum foraging strategies practiced hundreds of years earlier (22).

There is, then, a continuum between resource management, domestication, and agriculture. Although the existence of each precursor component of the continuum is essential for the development of the next, the development of any one of these different phenomena does not necessarily result in the development of the next. It is also difficult, along this continuum of closely related phenomena, to draw clear and sharply defined thresholds that separate one stage from the next. How much investment in tending a plant or animal or how much genetic or plastic response on the part of the plant or animal is needed before it can be said to have crossed the boundary between managed and domesticated? What percentage of overall caloric intake and labor investment in domesticates is needed before an economy can be identified as having transitioned from low-level food production to agriculture? Focusing on precise demarcation of such thresholds and establishing when, exactly, they have been crossed is a largely unproductive exercise that creates the erroneous impression of dichotomous states between wild and domestic, foraging and farming, and distracts attention from the often opaque, but far more interesting, middle-ground areas that lie between them. Rather than trying to define such thresholds, it is more productive to concentrate on the contexts and processes that shape behaviors involved in management, domestication, and agriculture and the evolutionary progression between them.

Thus, although management, domestication, and agriculture have overlapping elements, they are nonetheless distinct phenomena. The definitions proposed here focus on core aspects of each in a way that allows useful distinctions to be drawn between them. Management, as defined here, centers on the actions of the manager in attempting to enhance the returns of a resource of interest. The definition of domestication emphasizes the coevolving mutualism between the manager and the managed resource and the responses each make to promote this relationship. Agriculture is defined as a provisioning system in which the production and consumption of domesticates plays a dominant role. Defining these closely related terms in this way spotlights different key features of each, making it clear that each is the product of different circumstances influenced by different causal factors and best monitored using different types of markers.

Impacts and Markers

Although domestication should not be defined in terms of its impacts, identifying these impacts and understanding how they relate to the process of domestication is essential. Current research on domestication is, in fact, largely focused on identifying the impacts of domestication and using them as markers of the timing and nature this evolutionary transition in the distant past, as well as to monitor ongoing efforts at improving existing domesticates and creating new ones. Domestication produces a wide array of changes that vary in how directly they can be causally linked to the relationship between domesticator and domesticate. Establishing the existence and relative strength of such cause-and-effect linkages is important in determining the utility or value of different markers used to trace the initial development and subsequent evolution of domestication partnerships.

Genetic Impacts.

Genetic responses that maintain and enhance the domesticatory relationship are the most proximate result of domestication and, if clearly linked to this relationship, are its most compelling indicators. Genetic change can occur in both partners, especially when nonhuman species are the domesticators. When humans are involved, genetic change is almost always confined to the plant or animal partner species, with genetic impacts of domestication in humans only occasionally identified (23).

Genetic responses to domestication are the result of a number of different selective pressures. The two most important of these in early domesticates were most likely the relaxation of selective pressures experienced in a free-living state and the introduction of new selective factors arising from closer association with humans (15, 24). Once humans began to isolate managed resources from free-living populations, especially when they were moved outside of the natural range of their progenitors, both genetic drift and founder effects came into play. Directed or artificial selection through deliberate breeding to encourage specific traits is thought to be a relatively late development in most domesticates responsible for the appearance of “improvement traits” that follow initial domestication (25). It is, however, often hard to isolate any specific individual causal factors that result in particular genetic responses, with multiple selective pressures likely involved.

In both plants and animals there are constellations of traits that may not be the proximate result any of the selective pressures associated with the domestication process, but are instead linked to some other directly selected trait. In mammals this “domestication syndrome” includes lop ears, mottled coats, decreases in brain size, and changes in developmental rates—all traits that may all be linked to strong selection for lowered reactivity to external stimuli (15, 26). The appearance of this pleiotropic cascade of genetically driven traits may result from mutations in single genes responsible for the orchestration of gene expression during development (27). As a result only a small number of mutations in regulatory genes may be needed to account for many of the evolutionary changes that separate wild from domesticated plants and animals.

Full genome sequencing has vastly enhanced our ability to identify genes responsible for phenotypic changes that distinguish domesticates from their wild progenitors, with the greatest advances involving the identification of domestication genes in crop plants (28). Discovering key genes responsible for behavioral shifts in domestic animals has proven more difficult, although there have been some promising advances in this direction (29). Perhaps the most exciting work in documenting genetic change associated with early domestication involves ancient DNA extracted from archaeobiological remains and the resultant identification of the timing and sequence of the appearance of key domestication genes in both crops (30) and livestock (31).

The majority of genetic research on domestication has focused on neutral noncoding genes used to trace the phylogeny of domesticates. Early work concentrated on the chloroplast genome in plants and mitochondrial genome in animals (32). Studies of a single genome only tell one side of the story, however, and more recent nuclear genome sequencing technology has provided a much more complete picture of the heritage of domesticates. Nuclear genome research, for example, has demonstrated that what seemed to be multiple independent domestication events in various livestock species are more likely attributable to introgression between introduced domesticates and indigenous wild populations (25). Once again the most significant insights into the phylogenies of domesticates are gained through the analysis of ancient DNA, which promises a picture of the early divergence of domesticates from wild progenitors unclouded by the millennia of subsequent introgression and directed breeding (25, 33).

Phenotypic Impacts.

Genetically driven phenotypic changes in morphology, physiology, or behavior of emergent domesticates are one step removed from the selective factors operating on the genomes of domesticates. As a result there is a somewhat higher burden of proof in determining whether specific phenotypic traits in domestic crops and livestock are, in fact, the product of the domesticatory relationship and, if so, how and when they arose. The challenges in using these traits to trace domestication pathways are compounded by the fact that only a small portion of the phenotypic impacts of domestication are visible in the archaeological record.

In annual plants impacts of domestication are seen primarily in traits related to germination and dispersal—changes in dormancy rates, seed size, and testa thickness, as well as in the timing and morphology of dispersal mechanisms (14, 34). It had been thought that that the most archaeologically visible impacts of domestication in some annual plants (i.e., seed size increases and the loss of indehiscent structures for seed dispersal) would appear quite quickly with sustained human sowing and harvesting (35). Recent work, however, has shown that these responses may appear substantially later than other phenotypic changes. The appearance of nonshattering rachises in Near Eastern cereals, for example, is not, as once argued, a marker of the beginning of a domesticatory relationship with humans, but instead an artifact of changes in harvest technology and timing that occurred long after humans were actively engaged in sowing, cultivating, and harvesting cereals (34). Recent evidence also indicates that seed size increase in Near Eastern pulses only appeared after other responses to human cultivation occurred—the lowering of seed dormancy rates and the development of indehiscent seed pods, attributes that in pulses are not generally preserved in archaeobiological assemblages (36).

In contrast to annual plants, it has been argued that deliberate selection for desired traits played a significant early role in the domestication of perennial plants and tree species, especially those clonally propagated through vegetative cuttings (14, 37). Phenotypic responses in root crops and tubers, for example, are argued to include changes in the size, chemical, and starch composition of underground organs that made these plants more palatable and more profitable (38). In the absence of decay-resistant diagnostic parts, especially in the humid tropics where many of these crops were first domesticated, research has focused on the recovery of starches, which seem to display distinctive phenotypic responses to domestication in both morphology and their size (38). Although highly susceptible to postdepositional decay, starches can be recovered from the surface and interstitial cracks in chipped and ground stone and pottery and even in the calculus on human teeth (39).

Phytoliths are another microscopic plant component argued to have undergone genetically driven phenotypic change under domestication. Found in many annual and perennial crop plants, these opal silica bodies provide structural support, protect against predation, and are highly resistant to postdepositional decay under most conditions (40). As with starches, it is argued that there is a direct relationship between selection for larger fruit size and an increase in phytolith size, sometimes accompanied by distinctive changes in morphology—traits used as markers of domestication in a number of crop plants (41⇓–43).

The utility of microbotanical remains such as starches and phytoliths as markers of domestication is tempered by a number of factors. These include a lack of clarity about the linkage between selection forces on plants under domestication and observed differences in the size and morphology of starches and phytoliths (40), as well as difficulty in distinguishing domestication traits from those caused by factors unrelated to domestication (i.e., pathogens, soil substrate, water availability, and food preparation techniques) (44⇓⇓–47). Taphonomic issues surrounding the preservation and stratigraphic integrity of plant microfossils are not well understood (48). Uncertainties about the movement of phytoliths in soils, in particular, raise questions about the reliability of indirect dates of phytoliths recovered from archaeological deposits, and even direct radiocarbon dating of phytoliths may be affected by the sequestration of old carbon in phytoliths (49). Inconsistencies in the description and quantification of distinguishing criteria, especially uncertainty over inter- and intrataxa variability (48, 50), are cited as serious concerns limiting the utility and reliability of microfossils in documenting domestication that call for more conscientious publication of images of reference collections and archaeological assemblages (48) and freer access to assemblages by researchers seeking to replicate results.

In animals the earliest and most universal genetically driven phenotypic impacts of domestication focus on behavioral attributes, especially on endocrine-controlled behaviors that lower the animal’s reactivity to humans and facilitate its adaptation to an anthropogenic environment (15). These selective pressures are argued to result in brain size reduction in domestic animals (51), especially in those areas of the brain controlling endocrine function, that, as discussed above, are linked to pedomorphism in developmental rates and the retention of juvenile morphological characteristics in adult animals (15). The neotonization of domestic pig and dog cranial morphology attributed to this process is argued to have caused a decrease in prognathism that, in turn, is responsible for reduction in the size of teeth, crowding, and variations in tooth number—traits used as markers of initial domestication in these species (52, 53). It may be difficult, however, to tell whether these traits arose during an initial commensal phase as these animals moved into anthropogenic niches, rather than as responses to a later phase of active domestication.

Once thought a marker of initial domestication in sheep and goat, changes in horn morphology—linked to a relaxation of the selective advantage of large horns in mate competition, active selection against large horns no longer useful in securing mates, and perhaps deliberate directed selection by humans against aggressive large-horned males—are now known to have appeared after domesticates were moved out of the natural habitat of their wild progenitors, a millennia or more after clear signs that these animals were managed in ways consistent with domestic herds (54). The utility of body size reduction, once considered an essentially instantaneous product of domestication (55), has also been called into question. Apparent decreases in ovi-caprid body size at about 10,000 y ago are now known to be the result of demographic shifts in the archaeological assemblages of managed animals (dominated by smaller females) compared with assemblages composed of hunted animals (dominated by large prime-age males) (56).

Geometric morphometrics (GMM) is a relatively new and widely heralded technique for distinguishing between the teeth of wild and domestic pigs (31, 57⇓–59). Rather than the result of specific selective pressures, it is argued that subtle changes in tooth shape measured by GMM are proxies for the neutral genetic shifts used to trace the phylogenetic histories of domestic animals (18). Demonstration is still lacking, however, of how and why these changes in tooth shape track the genetic differentiation between wild and domestic taxa (60). If shape can to be shown to be a marker of phylogeny, the next challenge will be to determine how phylogenetic differentiation caused by domestication can be distinguished from other processes, (i.e., geographic barriers or habitat shifts) that also result in reproductive isolation and subsequent genetic differentiation. As with plant microfossils, issues of interanalyst comparability, quantification, and standardization need to be addressed before the potential of GMM in documenting domestication can be fully realized.

Plastic Impacts.

Domestication also results in plastic responses unrelated to genetic responses to the new selective pressures experienced under domestication, or their phenotypic expression. Nonetheless, plastic responses to domestication may be both numerous and dramatic and, as a result, can provide significant information regarding the domestication process. In humans, these “ecophenotypic” responses include: contraction of zoonotic diseases carried by domestic animals; changes in stature or growth rates; increased prevalence of dental caries owing to greater reliance on carbohydrate-rich crop plants; changes in bone chemistry reflecting dietary shifts; and biomechanical stresses on human skeletons from tending domesticates (61). In animals proposed domestication-induced plastic responses include: dental irregularities (hypoplasias) caused by nutritional and other stresses experienced under human management; diseases that cause large fetal and neonatal mortality; bone chemistry changes owing to provision of forage or changes in the mobility; and pathologies arising from tethering, use as draft animals, riding, or carrying heavy loads (62⇓⇓–65). Plastic responses in plants that arise as a consequence of human cultivation are fewer and include possible responses to artificial watering that increase the plumpness of cereal grains or affect the size and aggregation of phytoliths, as well as chemical responses to field conditions (66⇓–68).

The linkage of plastic responses to domestication, however, is more difficult to differentiate from other causal factors unrelated to domestication. It is also difficult to identify at what point these responses become manifest, with many arising after domesticates become the underpinnings of agricultural economies.

Impacts on Natural and Cultural Contexts.

Impacts of domestication are also seen in the natural and cultural settings in which the evolving relationship takes place. Human niche-constructing activities directed at enhancing the yield or predictability of resources of economic interest that are prerequisites for domestication may have profound impacts on natural environments. These activities include: modifying vegetative communities through burning to increase abundance of herbaceous plants and animals of economic importance; modifying landscapes to enhance water delivery or expand habitat zones of plants and sessile animals; broadcast sowing of wild annuals near water sources; transplanting perennial fruit-bearing species nearer to settlements; and selectively culling competing vegetation to encourage the growth of fruit- and nut-bearing trees (69, 70). Increases in the abundance of an animal species in the archaeological record may result from efforts that promote population growth (i.e., burning), or through the construction of structures that facilitate capture (i.e., fish weirs or kites) (69, 71). Efforts at enhancing access to economically important animals also find expression in harvest strategies designed to increase prey availability that may lead to active management of animal populations and domestication (54, 56).

Evolving relationships between humans and target plant and animal species also have enduring impacts on the cultural setting in which these relationships developed. Tending plants and animals and storing resources they produce may find expression in the built environment (appearance of corrals, storage pits, or silos, the presence of manure and its use as a fuel or building material) that may be used to trace the increasingly close relationships between humans and managed resources (72, 73). Greater investment in resource management may strengthen notions of ownership over resources and the catchment areas in which they are grown and harvested, resulting in more tightly defined and defended territories (74). Alterations in labor relations, in access to resources within communities, in mechanisms for maintaining community cohesion, and even in beliefs about the relationship between humans and the natural world have all accompanied increasing human investment in emergent domesticates in ways that have found expression in the archaeological record (75).

Impacts on natural and cultural settings, however, may be especially hard to link to domestication. The effects of resource management on natural settings are difficult to detect and, if detected, difficult to distinguish from natural forces (70). Arguments for human involvement in the movement of domesticates beyond the geographical range of their wild progenitors based on modern distributions may not reliably reflect ancient distributions (54, 76). Cultural responses to increasing engagement in managing plants and animals may vary and may arise in the absence of domesticates. Whereas many of the archaeological markers resulting from these impacts can be used to detect resource management, they are not necessarily indicative of the development of a domesticatory relationship between humans and managed species. This requires demonstrating the existence of a sustained coevolving mutualism between humans and target species.

This is not to say that evidence of genetic or resulting phenotypic change necessarily takes priority over other markers. The detection of “domestication” genes controlling coat color among pigs recovered from forager settlements in northern Europe, for example, does not indicate that these hunter-gatherers “possessed” domestic pigs or that these were “the earliest domestic animals” in this region (57, 77). Rather, it indicates that these pigs had some degree of domestic ancestry, likely acquired through introgression between escaped domestic pigs from nearby farming communities and indigenous wild boar (60, 78). In addition to genetic markers, establishing the domestic status of these animals would require some evidence that foragers were engaged in an ongoing domesticatory relationship with the pigs in question, based on, for example, harvest profiles, evidence of penning, or nutritional changes indicative of active human management.

No one marker—genetic, phenotypic, plastic, or contextual—is sufficient to definitively document domestication. Because domestication is a multifaceted relationship involving both biological and cultural processes, documenting it requires looking across a wide range of markers and tracking how and when they are manifested. Fortunately, methods for tracing multiple markers of domestication up through time have been developing at a rapid pace and, as a result, there are now relatively high-resolution records of the origins and evolution of plant and animal domestication in a number of world areas. These increasingly detailed regional-scale developmental sequences are making it possible for researchers to better address the most difficult of the core questions of domestication research: why these relationships arose in the first place.

Causal Factors

Early causal explanations for domestication conflated domestication and agriculture, and focused on identifying single factors that were thought to account for both phenomena (79). These “prime-mover” explanations can be grouped into “push” and “pull” scenarios. Push scenarios set developments in the context of external stresses that forced people to domesticate and adopt agricultural practices—factors such as climate change or population increase. Pull scenarios were usually set in more benign, even bountiful, contexts, emphasizing internal factors that encouraged humans to adopt these practices—an interest in social promotion or cognitive changes in how people view their relationship to the natural world (75).

Such single-factor scenarios were easier to advance when the outlines of domestication and agricultural origins in various world areas were poorly documented. The high-resolution regional-scale records that are now becoming available, however, indicate that these developments were shaped by a number of complex and locally contingent factors that cannot be accounted for by single-factor explanatory frameworks (79). As a result, attention has shifted toward identifying broader contextual frames of reference within which different regional trajectories of domestication and agriculture have unfolded. The long delay between initial domestication and the development of agriculture in different independent regions (20, 76) also makes it clear that a single explanatory framework cannot account for both the origins of domestication and the subsequent emergence of agriculture. Although the descriptive gloss “origins of agriculture” or “OA” is sometimes still used (10), almost all current research is focused not on agricultural origins but on initial domestication (76). Two alternative explanatory frameworks for initial domestication have recently drawn considerable attention. Although both are characterized as grounded in evolutionary biology, they draw on very different paradigms and offer oppositional explanatory accounts.

For over a decade researchers endorsing optimal foraging theory (OFT) have argued that goals of optimizing energetic returns were primary shaping factors in domestication (80⇓⇓–83). Characterized as derived from neo-Darwinian evolutionary theory, OFT is based on the premise that optimizing behaviors confer a selective advantage to individuals who practice them. Of the various OFT models that have been developed, only the diet breadth model (DBM) has been used in efforts to explain initial domestication (10). DBM predicts that foragers will always choose resources with higher net energy returns, after search and processing costs, over lower return resources. Items are added to the diet in descending rank order, with items falling below a certain level of return always ignored, regardless of their abundance, as long as there is a reasonable expectation of the availability of higher-ranked resources. The model further predicts that when high-ranking resources are abundant, diet breadth will narrow and foraging efficiency will increase. Conversely, when availability of high-ranked resources decreases, diet breadth will broaden because a wider range of lower-ranked resources will be added to the diet to compensate for reduced access to higher-ranked resources, resulting in an overall lowering of foraging efficiency. Moreover, under DBM rules foragers will only opt for resources with delayed returns (resources that require tending over a growth cycle) when resources that provide immediate returns are no longer as plentiful.

Because domestication frequently focuses on resources OFT proponents identify as low-ranking—plants and small to medium-size mammals (10)—the addition of progenitors of future domesticates to forager diets is automatically cast as a response to lowered availability of higher-ranking resources (i.e., larger game animals). Moreover, because management of these resources entails a system of delayed returns, the impetus for increasing engagement in management is also, by definition, a response to continued resource pressure that precludes a return to the immediate-return strategies focused on high-ranked resources. Such DBM-derived explanations for initial domestication represent a recent incarnation of stress-based or “push” prime-mover models, providing a framework in which resource depression, environmentally or demographically induced, accounts for the addition of domesticate progenitors into the diet and their subsequent domestication.

In direct opposition to DBM-based explanatory frameworks, a cultural niche construction (CNC) explanatory framework for initial domestication is directly derived from macroevolutionary theory (69, 74, 76, 84⇓–86). In contrast to a neo-Darwinian focus on selection-driven allele frequency changes in individual organisms, macroevolutionary theory considers organisms as integrated wholes that do not simply adapt to changes in their environment but that may, through more hierarchical and interactive processes, actually shape their environments (23). This is accomplished through niche construction or ecosystem engineering, with organisms acting “as co-directors of their own and other species evolution” (87). Although many organisms engage in niche-constructing activities, humans, with their ability to spontaneously invent and modify new goal-directed behaviors and pass them on through cultural transmission, are considered the “ultimate niche constructors” (84, 88). These are the behaviors that CNC explanatory frameworks hold central to the domestication of plants and animals.

Whereas OFT explanatory frameworks cast efforts at modifying environments leading to domestication as adaptive responses to resource depression (81, 83), CNC explanatory frameworks see niche construction as an important driver of evolutionary change that does not require resource depression to be set into motion. In fact, a CNC approach argues that long-term commitments to niche-constructing activities required for domestication are more likely to occur in stable or resource-rich environments (76, 86). So, whereas OFT scenarios place domestication in the context of imbalances between population and a region’s carrying capacity (10), CNC explanatory frameworks argue that stable to resource rich environments made it possible for human groups to abandon more mobile strategies and establish relatively permanent communities that served as the nexus for the increase and dissemination of information about the environment, each other, and the broader world (86). Environments with abundant, diverse resources predictably found within well-defined resource catchment territories provided particularly productive platforms for the development of broad-based subsistence economies capable of supporting larger and more permanent communities. Stable, resource-rich environments also provided opportunities for experimentation with different productivity-enhancing exploitation techniques (74, 86). At the same time other species took advantage of newly created anthropogenic niches, fostering new relationships with humans. Long-term investment in these environments served as an added incentive for human groups to defend resource catchment territories and continue to enhance the growing store of ecological knowledge that allowed communities to continue to reap the rewards of previous generations’ investment in modifying and shaping these environments (74).

CNC explanatory frameworks are similar in some respects to earlier pull scenarios in that, in contrast to DBM explanations, they include an important social element—although in this case forces enhancing social cohesion are emphasized over those that promote differential access to resources. However, unlike earlier pull explanations that tend to cast social and ideological factors as sole drivers of the process at the expense of environmental or economic considerations, a CNC approach demonstrates how, in the context of resource-rich environments, goals of preserving community cohesion and longevity combine with complementary goals of creating a secure and predictable resource base, producing natural and cultural contexts in which niche-constructing activities lead to the development of domesticatory relationships between humans and target plant and animal species.

OFT-derived explanatory frameworks for domestication have recently been characterized as superior to other explanatory approaches based on their supposed purer scientific pedigree and the shortcomings of alternatives, including those derived from niche-construction theory, which are described as a “hodgepodge” of inductively derived particularistic just-so stories that represent a “retreat from theory” (10). Explanations derived from DBM are characterized as providing compelling accounts for “agricultural origins” (initial domestication) that are well supported by empirical data in two of the world’s independent centers of domestication, the Neotropics and southwest Asia. A third center where DBM is acknowledged as failing to explain domestication, eastern North America, is argued nonetheless to be in accordance with other models based on core OFT optimizing principles. Closer scrutiny, however, shows that DBM/OFT explanatory frameworks lack empirical support in all three of these centers of domestication (76, 79, 86).

In the Neotropics, for example, climate-induced resource depression in the form of late Pleistocene megafaunal extinction is identified as forcing human foragers to adapt by expanding their diet to include lower-ranking root crops, which were then domesticated (83). Recent research, however, indicates that megafauna disappeared from northern South America a full 3,000 y before initial human occupation of the region, and 5,000 y before the earliest evidence for domesticates (76, 89). In addition, a proposed northern South America center of domestication of more than a dozen root crops is situated not in the savanna/dry shrub environment of Pleistocene megafauna, but rather in the seasonal dry forests of inter-Andean river valleys—environments that did not witness any apparent decline in resource availability leading up to initial domestication (76, 90).

Similarly, DBM-based explanations for the increase in dietary diversity and resource intensification leading up to initial domestication in the Levantine region of southwest Asia are based on troubling tautologies that interpret the loss of mobility as evidence for the causal role of population packing in the loss of mobility, and the diversification in the dietary resources as an indication of the role of resource depression in causing resource diversification (81, 91). In the eastern areas of the Fertile Crescent where three major livestock species and a number of crop plants were initially domesticated (21), even OFT proponents admit that there is no evidence for either population packing or resource depression (92).

Finally, claims that OFT practitioners have engaged in a rigorous “hypothetical-deductive” program of “theoretically driven hypothesis testing” in eastern North America, where DPM predications are not supported by empirical data (10, 82), are instead examples of post hoc theorizing in which one OFT-derived model is replaced with another without further testing or consideration of other models that lie outside OFT optimizing precepts (76).

However, there is abundant evidence that would support alternative CNC-informed explanatory frameworks for initial domestication in all three regions (76, 79, 86). Initial domestication in each takes place in the context of foraging communities situated in river valley catchments with easy access to multiple ecozones supporting an array of abundant and predictably available resources. There is also ample evidence for a protracted period of human enhancement of environments that preceded initial domestication in each region—evidence of anthropogenic fires resulting in shifts in forest composition, as well as increased availability of high-value plant and animal species that moved into newly created anthropogenic environments (76, 82, 90, 93⇓–95).

The relative value of these two very different explanatory approaches to initial domestication can now be determined through side-by-side comparison in an expanding number of world areas where enhanced methods for tracking the impacts of evolving domesticatory relationships are producing detailed empirical records of these evolutionary transitions (76, 86). Advancing our understanding of the causal context of domestication, however, will be based on conscientious comparison of alternative explanatory frameworks with empirical reality, rather than the polemics and posturing that often accompany the defense of favored paradigms.

Relevance

A final question to be addressed is whether defining domestication, identifying its impacts, and exploring the reasons why humans and certain plant and animal species first entered into domesticatory relationships has any relevance to current pressing issues concerning domesticates and their role in feeding the world’s growing populations. The answer is, quite simply, yes. Understanding how plant and animal species respond to varying levels of human manipulation is directly relevant to ongoing efforts at improving existing crops and livestock and bringing new and ever more challenging species with greater innate barriers to domestication under human control. Tracing the pathway that humans took to become primary drivers of earth systems, ushering in the Anthropocene, begins with human efforts at ecosystem engineering that led to initial domestication of plants and animals more than 10,000 y ago and created the platform for the agricultural economies that have transformed Earth’s biota, landforms, and atmosphere and the trajectory of human cultural evolution (96). A look backward at the ways in which humans and their domesticate partners created anthropogenic landscapes that both sustained and enhanced ecosystems around the world and, at times, rendered them uninhabitable for organisms living outside human ecoengineered systems, has direct relevance for understanding present-day issues of sustainability and biodiversity loss. Finally, exploring core concepts of domestication provides an unparalleled opportunity to examine the interface between humans and the natural world and how processes that shape human cultural evolution interact with those governing biological evolution.

Achieving the full potential of domestication research requires a broadly transdisciplinary approach that brings together genetics, evolutionary biology, ecology, and anthropology in ways that promise exciting new insights regarding the coevolution of coupled human and natural systems. Asking the fundamental questions about domestication addressed here—what it is, what is does, and why it happens—provides a unifying framework that grounds diverse and far-ranging research reaching from the initial steps human and plant and animal partners followed into domesticatory relationships up to the present day and beyond.

Acknowledgments

I thank Gary Crawford, Edwård Fisher, Fiona Marshall, and Bruce Smith for helpful comments on this paper.

Footnotes

• ↵1Email: zederm@si.edu.

• This contribution is part of the special series of Inaugural Articles by members of the National Academy of Sciences elected in 2012.

• Author contributions: M.A.Z. designed research and wrote the paper.

• Reviewers: G.W.C., University of Toronto Mississauga; and F.B.M., Washington University in St. Louis.

• The author declares no conflict of interest.

• This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1501711112/-/DCSupplemental.

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